It is proposed to investigate, in a systematic and detailed fashion, the redox and associated chemical reactions of biologically important pteridines using a variety of electrochemical, spectral and chemical techniques. The principle objective of the planned work is to understand the redox chemistry of reduced or so-called unconjugated pteridines such as tetrahydrobiopterin and tetrahydrofolic acid by investigating the electrochemistry of these and appropriately related model tetrahydropteridine systems. As a result of the planned electrochemical spectroelectrochemical and chemical studies of such compounds we expect to characterize the electrode potentials associated with their electron-transfer reactions, the intermediates formed in these redox reactions and the chemical reactions of these intermediates to form the observed reaction products. Such information should have direct relevance to the redox behavior of such molecules in biological systems for example in their role as cofactors in various enzymatic hydroxylation processes. It is also planned to initiate some studies of the electrochemical oxidation of so-called conjugated pteridine systems of biological interest.